SiO2-functionalized melamine-pyridine group-supported Cu(OAc)2 as an efficient heterogeneous and recyclable nanocatalyst for the N-arylation of amines through Ullmann coupling reactions

This study reports a convenient approach to prepare SiO2/CCPy/Cu(OAc)(2) as a novel nanocatalyst, in which melamine-bearing pyridine groups have functionalized SiO2 and can act as a capping agent to stabilize Cu(II) species. The catalyst is characterized through Fourier transform infrared, transmission electron microscopy, field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET), thermogravimetric analysis, inductivity coupled plasma (ICP), and energy dispersive X-ray (EDX) techniques. Furthermore, its catalytic behavior is evaluated in the N-arylation of indole, imidazole, and aniline during Ullmann-type C-N coupling reactions. Moreover, it has been proved that the heterogeneous nanocatalyst can be feasibly recovered by filtration and reused in five consecutive reaction cycles without any noticeable loss of its catalytic activity. The results clarified that the devised method is advantageous from several perspectives, that is, low catalyst loading, high product yield, experimental simplicity, broad substrate scope, and short reaction time. (C) 2018 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.